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[thirdparty/glibc.git] / math / s_ctanh.c

diff --git a/math/s_ctanh.c b/math/s_ctanh.c
index 201871e7ec5e54a9cb65845de5f629831563494d..0ca35e09902f2602dbf612702dfaaaad8154f1c2 100644 (file)
--- a/math/s_ctanh.c
+++ b/math/s_ctanh.c
@@ -1,5 +1,5 @@
 /* Complex hyperbole tangent for double.
-   Copyright (C) 1997-2012 Free Software Foundation, Inc.
+   Copyright (C) 1997-2014 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
 
@@ -53,11 +53,20 @@ __ctanh (__complex__ double x)
       double sinix, cosix;
       double den;
       const int t = (int) ((DBL_MAX_EXP - 1) * M_LN2 / 2);
+      int icls = fpclassify (__imag__ x);
 
       /* tanh(x+iy) = (sinh(2x) + i*sin(2y))/(cosh(2x) + cos(2y))
         = (sinh(x)*cosh(x) + i*sin(y)*cos(y))/(sinh(x)^2 + cos(y)^2).  */
 
-      __sincos (__imag__ x, &sinix, &cosix);
+      if (__builtin_expect (icls != FP_SUBNORMAL, 1))
+       {
+         __sincos (__imag__ x, &sinix, &cosix);
+       }
+      else
+       {
+         sinix = __imag__ x;
+         cosix = 1.0;
+       }
 
       if (fabs (__real__ x) > t)
        {
@@ -83,10 +92,22 @@ __ctanh (__complex__ double x)
        }
       else
        {
-         double sinhrx = __ieee754_sinh (__real__ x);
-         double coshrx = __ieee754_cosh (__real__ x);
+         double sinhrx, coshrx;
+         if (fabs (__real__ x) > DBL_MIN)
+           {
+             sinhrx = __ieee754_sinh (__real__ x);
+             coshrx = __ieee754_cosh (__real__ x);
+           }
+         else
+           {
+             sinhrx = __real__ x;
+             coshrx = 1.0;
+           }
 
-         den = sinhrx * sinhrx + cosix * cosix;
+         if (fabs (sinhrx) > fabs (cosix) * DBL_EPSILON)
+           den = sinhrx * sinhrx + cosix * cosix;
+         else
+           den = cosix * cosix;
          __real__ res = sinhrx * coshrx / den;
          __imag__ res = sinix * cosix / den;
        }